This invention relates to surgical manipulators and more particularly to robotically-assisted apparatus for use in surgery.
In standard laparoscopic surgery, a patient""s abdomen is insufflated with gas, and trocar sleeves are passed through small (approximately xc2xd inch) incisions to provide entry ports for laparoscopic surgical instruments. The laparoscopic surgical instruments generally include a laparoscope for viewing the surgical field, and working tools such as clamps, graspers, scissors, staplers, and needle holders. The working tools are similar to those used in conventional (open) surgery, except that the working end of each tool is separated from its handle by an approximately 12-inch long extension tube. To perform surgical procedures, the surgeon passes instruments through the trocar sleeves and manipulates them inside the abdomen by sliding them in and out through the sleeves, rotating them in the sleeves, levering (i.e., pivoting) the sleeves in the abdominal wall and actuating end effectors on the distal end of the instruments.
In robotically-assisted and telerobotic surgery (both open and endoscopic procedures), the position of the surgical instruments is controlled by servo motors rather than directly by hand or with fixed clamps. The servo motors follow the motions of a surgeon""s hands as he/she manipulates input control devices and views the operation via a displayed image from a location that may be remote from the patient. The servo motors are typically part of an electromechanical device or surgical manipulator that supports and controls the surgical instruments that have been introduced directly into an open surgical site or through trocar sleeves into a body cavity, such as the patient""s abdomen. During the operation, the surgical manipulator provides mechanical actuation and control of a variety of surgical instruments, such as tissue graspers, needle drivers, etc, that each perform various functions for the surgeon, i.e., holding or driving a needle, grasping a blood vessel or dissecting tissue.
This new method of performing telesurgery through remote manipulation will create many new challenges. One such challenge is transmitting position, force, and tactile sensations from the surgical instrument back to the surgeon""s hands as he/she operates the telerobotic system. Unlike other techniques of remote manipulation, telesurgery can give the surgeon the feeling that he/she is manipulating the surgical instruments directly by hand. For example, when the instrument engages a tissue structure or organ within the patient, the system should be capable of detecting the reaction force against the instrument and transmitting this force to the input control devices. In this manner, the surgeon can see the instrument contacting the tissue structure on the displayed image and directly feel the pressure from this contact on the input control devices. Providing the appropriate feedback, however, can be problematic because of other forces acting on the system, such as friction within the telerobotic mechanisms, gravity and inertial forces acting on the surgical manipulator or forces exerted on a trocar sleeve by the surgical incision.
In addition, to enable effective telesurgery, the manipulator must be highly responsive and must be able to accurately follow even the most rapid hand motions that a surgeon frequently uses in performing surgical procedures. To achieve this rapid and responsive performance, a telerobotic servo system must be designed to have an appropriately high servo bandwidth which requires that the manipulator be designed to have low inertia and to employ drive motors with relatively low ratio gear or pulley couplings.
Another challenge with telesurgery results from the fact that a portion of the electromechanical surgical manipulator will be in direct contact with the surgical instruments, and will also be positioned adjacent the operation site. Accordingly, the surgical manipulator may become contaminated during surgery and is typically disposed of or sterilized between operations. Of course, from a cost perspective, it would be preferable to sterilize the device. However, the servo motors, sensors and electrical connections that are necessary to robotically control the motors typically cannot be sterilized using conventional methods, e.g., steam, heat and pressure or chemicals, because they would be damaged or destroyed in the sterilization process.
What is needed, therefore, is a robotically-assisted apparatus for holding and manipulating surgical instruments by remote control. The apparatus should be configured for easy sterilization so that it can be reused after it has been contaminated during an operation. The apparatus should be further capable of providing the surgeon with the appropriate feedback from forces transmitted to and from the surgical instrument during the telerobotic operation and it should be configured to compensate for gravitational forces acting on the apparatus so that these forces are not felt by the surgeon. In addition, the apparatus must be highly responsive and must be able to accurately follow even the most rapid hand motions that a surgeon frequently uses in performing surgical procedures.
According to the invention, an apparatus is provided for holding and manipulating a surgical instrument during conventional open surgery or endoscopic procedures, such as laparoscopy. The apparatus comprises a support base fixable by means of various passive or power driven positioning devices to a surface, such as an operating table, and an instrument holder movably mounted on the base. The instrument holder comprises a body and an instrument support movably coupled to the body and having an interface engageable with the surgical instrument to releasably mount the instrument to the instrument holder. A drive assembly is operatively coupled to the instrument holder for providing the instrument with at least two degrees of freedom. The drive assembly includes a first drive for moving the instrument support and a second drive for moving the instrument holder relative to the support base. The apparatus includes means for removably coupling the instrument holder from the base and the drive assembly so that the holder can be separated from the rest of the device and sterilized after a surgical procedure.
In a specific configuration, the support base includes a frame with distal and proximal support members and a pair of shafts rotatably mounted within the support members. The instrument holder is slidably mounted on the support shafts for axial movement of the instrument. In addition, the shafts are each coupled to a drive motor for providing the instrument with second and third degrees of freedom, e.g., rotation and end effector actuation. The drive motors are coupled to the proximal support member so that they will not be contaminated during surgery. The rotatable shafts can be removed by sliding them upward and out of engagement with their lower bearings and the instrument holder so that the instrument holder can be easily removed from the support base for sterilization. The lower portion of the support base (including the distal support member) may also be sterilized to decontaminate those parts that have contacted the instrument holder. In this manner, the surgical manipulator can be easily sterilized after a surgical procedure without damaging the servo motors or the electrical connections required for the telerobotic system.
The support base further comprises a sleeve, such as a cannula or trocar sleeve, mounted on the distal support member. The sleeve has an axial passage for receiving the instrument therethrough and a force sensing element mounted within the axial passage near the distal end of the sleeve. The force sensing element is configured to detect lateral forces exerted on the element by the distal portion of the instrument during surgery. Since the force sensing element is mounted distal to the remainder of the apparatus, it is undisturbed by forces that may be exerted on the cannula by the surgical incision or by gravity and inertial forces that act on the instrument holder. When supported by a positioning device, the surgical manipulator can be used with an inclinometer to determine the true orientation of the instrument holder with respect to the direction of the local gravitational field. Use of the inclinometer and force sensors with the manipulator facilitates the design of a telerobotic system in which the surgeon will directly sense the forces acting against the end of the instrument, unaffected by extraneous forces acting on the telerobotic mechanism. In other words, the surgeon will feel as if his/her hands are holding the instrument at the point in which the instrument contacts the force sensing element.
The invention is particularly useful for holding and manipulating a surgical instrument having an end effector, such as a pair of jaws, coupled to the distal end of the instrument shaft. To that end, the instrument holder further includes an actuator driver having an interface engageable with an end effector actuator on the instrument. The actuator driver includes a coupling that connects the driver to the drive assembly for axially moving a portion of the driver relative to the support base, thereby actuating the end effector of the instrument. In a preferred configuration, the coupling is a concentric helical actuator that translates rotation from a drive motor into axial movement of the end effector actuator. Because of the symmetrical design of the helical actuator, the actuation force applied by the drive motor will not generate any effective side loads on the instrument, which avoids frictional coupling with other degrees of freedom such as axial movement and rotation of the instrument.
Other features and advantages of the invention will appear from the following description in which the preferred embodiment has been set forth in detail in conjunction with the accompanying drawings.